Find research datasets worth reusing

opencc-by-4.0Oct 2020View details →

The anisotropy in the optical constants of quartz crystals for soft X-rays

The refractive index of a y-cut SiO2 crystal surface is reconstructed from polarization dependent soft X-ray reflectometry measurements in the energy range from 45 eV to 620 eV. In the datasets the 1-delta and beta values for the (100) and (001) direction of the SiO2 crystal for the different energies are provided.

opencc-by-4.0Jan 2021View details →

Dataset: Aberration characterisation of X-ray optics using multi-modal ptychography and a partially coherent source

These are the ptychography datasets used for the publication "Aberration characterisation of X-ray optics using multi-modal ptychography and a partially coherent source". File are in the HDF format and contain a number of datasets detailed below. If you require more information, please contact the corresponding author of the publication, at thomas.moxham@eng.ox.ac.uk Raw files contain: diffraction intensities, scanning positions in millimeters Recon files contain: fourier error, complex probe function, complex object function, recon pixel size, energy raw_siemens_star_be_lens.hdf, raw_fourier_ring_correlation.hdf, merlin_medipix_detector_mask.hdf, recon_multi-modal_probe.hdf, recon_multi-modal_object.hdf, recon_fourier_ring_correlation.hdf

opencc-by-4.0Mar 2022View details →

Optical and X-ray data on V496 UMa

The optical light curves and X-ray spectra and light curves presented in Kennedy et al. 2022 are given here. The code to reproduce the MCMCs  and plots from the paper is given in a github repo.

opencc-by-4.0Aug 2023View details →

Links Between Optical and X-ray Light in Scorpius X-1

Optical data taken from the Argos photometer in 2006.

zenodo32/100

Dataset for: Dynamically patterning X-ray beam by a femtosecond optical laser

This record contains the image and plot data for the paper "Dynamically patterning X-ray beam by a femtosecond optical laser".

opencc-by-4.0Jan 2024View details →

nasa24/100

The Focusing Optics X-ray Solar Imager (FOXSI): Update & Second Launch Project

Particle acceleration in solar flares and its contribution to coronal heating are among the main&nbsp; unsolved problems in heliophysics. Accelerated electrons in a plasma radiate hard X-ray (HXR)&nbsp; emission through the well-known process of bremsstrahlung. HXR observations therefore are a&nbsp; powerful diagnostic tool, providing quantitative measurements of flare-accelerated electrons. Since&nbsp; bremsstrahlung emission depends on the density of the ambient medium, solar HXR emission is&nbsp; usually brightest from below the transition region, where the density increases rapidly towards the&nbsp; photosphere. Electron beams entering the chromosphere lose energy quickly through collisions and&nbsp; produce relatively intense HXR emission at the footpoints of magnetic field lines. Electron beams&nbsp; moving in the relatively tenuous corona suffer very few collisions, losing little energy and producing&nbsp; only faint HXR emission. Present-day HXR instrumentation does not have the sensitivity to see&nbsp; faint HXR emission from electrons traveling in the corona, nor the dynamic range to see such&nbsp; faint emission in the presence of bright HXR footpoint emission in the chromosphere. Existing&nbsp; observations therefore show us only where energetic electrons are stopped, but not where they&nbsp; are accelerated, nor along what path they escape from the acceleration site. The most sensitive&nbsp; solar HXR observations so far are provided by the Reuven Ramaty High Energy Spectroscopic&nbsp; Imager (RHESSI) (Lin et al. 2002). These measurements are obtained with a non-focusing rotation&nbsp; modulation collimator (RMC) imaging technique (Hurford et al. 2002). RMCs and other types&nbsp; of non-focusing imaging, however, have intrinsically limited dynamic range and sensitivity. HXR&nbsp; focusing optics can overcome both of these limitations (Section 1.2.2).&nbsp; The Focusing Optics X-ray Solar Imager (FOXSI) is a sounding rocket payload funded under the&nbsp; NASA Low Cost Access to Space (LCAS) program to test HXR focusing optics combined with&nbsp; silicon strip detectors for solar observations (Krucker et al. 2009). The FOXSI program is being led&nbsp; by the Space Sciences Laboratory at UC Berkeley in collaboration with the Marshall Space Flight&nbsp; Center (MSFC) and the Japan Aerospace Exploration Agency (JAXA). FOXSI is on schedule&nbsp; and on budget for a launch in October 2010. FOXSI will offer imaging spectroscopy and&nbsp; unprecedented HXR sensitivity and dynamic range. FOXSI will be !100 times more sensitive than&nbsp; RHESSI at 10 keV, and, for the first time, detect the non-thermal counterparts of quiet sun network&nbsp; flares (Section 1.2.4).&nbsp; Here we propose a continuation of the FOXSI program which includes data analysis&nbsp; and a second flight with an upgraded version of FOXSI. At moderate cost, we propose to&nbsp; enhance the effective area, in particular at higher energies (by a factor of !4 at 15 keV), by adding&nbsp; 3 more shells to the existing 7-shell optics (see Figure 9). Furthermore, our Japanese collaborators&nbsp; will provide, at no cost, newly available double-sided cadmium telluride (CdTe) detectors as&nbsp; a replacement for the Si detectors to allow us to take full advantage of the effective area at higher&nbsp; energies. A second flight will therefore not only allow us to continue testing HXR focusing&nbsp; optics for solar observations and also test newly developed CdTe strip detectors&nbsp; in flight but is also expected to provide a significant increase in scientific return. In&nbsp; this two year proposal, the first year (2011) will be used to upgrade the FOXSI payload and to&nbsp; analyze data from the first flight, while the second flight is planned for the midd

restrictednotspecifiedMar 2025View details →

ROSAT International X-Ray/Optical Survey Source Catalog

The ROSAT International X-Ray/Optical Survey (RIXOS) is a medium-sensitivity survey and optical identification program for X-ray sources which were discovered in ROSAT high Galactic latitude fields (|b| > 28 degrees) and observed with the Position Sensitive Proportional Counter (PSPC) detector. The survey made use of the central 17 arcmin of each ROSAT field. A flux limit of 3 x 10-14 erg/s/cm2 (0.5-2.0 keV) was adopted for this survey, and a minimum exposure time of 8000 seconds was required for qualifying ROSAT observations. X-ray sources in the survey are therefore substantially above the detection threshold of each field used, and many contain enough counts to allow the X-ray spectral slope to be estimated. Spectroscopic observations of potential counterparts were obtained of all sources down to the survey limit in 64 fields, totaling a sky area of 15.77 square degrees. Positive optical identifications are made for 94% of the 296 sources thus examined. A further 18 fields (4.44 sq deg), containing 105 sources above the 3 x 10-14 erg/s/cm2 survey limit, are completely optically identified to a higher flux of 8 x 10-14 erg/s/cm2 (0.5-2.0 keV). Optical spectroscopic data are supplemented by deep CCD imaging of many sources to reveal the morphology of the optical counterparts, and objects too faint to register on Sky Survey plates. The faintest optical counterparts have R ~ 22. This table contains the catalog of the RIXOS sources and their optical identifications. This table was originally ingested by the HEASARC in June 2005 based on CDS table J/MNRAS/311/456/rixos.dat. It was updated in November 2013 shortly after the CDS released an update with the previously inadvertently omitted source RX J111809.9+212554 (RIXOS 123_84) included. This is a service provided by NASA HEASARC .

ELAIS S1 Field X-Ray Source Optical/IR Identifications Catalog

This table contains the optical identifications and a multi-band catalog of a sample of 478 X-ray sources detected in the XMM-Newton and Chandra surveys of the central 0.6 deg2 of the ELAIS-S1 field. The most likely optical/infrared counterpart of each X-ray source was identified using the chance coincidence probability in the R and IRAC 3.6 micron bands.This method was complemented by the precise positions obtained through Chandra observations. The authors were able to associate a counterpart to each X-ray source in the catalogue. Approximately 94% of them are detected in the R band, while the remaining are blank fields in the optical down to R ~ 24.5, but have a near-infrared counterpart detected by IRAC within 6 arcsec of the XMM-Newton centroid. The multi-band catalog, produced using the positions of the identified optical counterparts, contains photometry in ten photometric bands, from B to the MIPS 24 micron band. The spectroscopic follow-up allowed us to determine the redshift and classification for 237 sources (~ 50% of the sample) brighter than R = 24. The spectroscopic redshifts were complemented by reliable photometric redshifts for 68 sources. The authors classified 47% of the sources with spectroscopic redshift as broad-line active galactic nuclei (BL AGNs) with z = 0.1-3.5, while sources without broad-lines (NOT BL AGNs) are about 46% of the spectroscopic sample and are found up to z = 2.6. The remaining fraction is represented by extended X-ray sources and stars. The authors spectroscopically identified 11 type 2 QSOs among the sources with F(2-10 keV)/F(R) > 8, with redshift between 0.9 and 2.6, high 2-10 keV luminosity (log L(2-10 keV) >= 43.8 erg/s) and hard X-ray colors suggesting large absorbing columns at the rest frame (log NH up to 23.6 cm-2). BL AGNs show on average blue optical-to-near-infrared colors, softer X-ray colors and X-ray-to-optical colors typical of optically selected AGNs. Conversely, narrow-line sources show redder optical colors, harder X-ray flux ratio and span a wider range of X-ray-to-optical colors. On average the Spectral Energy Distributions (SEDs) of high-luminosity BL AGNs resemble the power-law typical of unobscured AGNs. The SEDs of NOT BLAGNs are dominated by the galaxy emission in the optical/near-infrared, and show a rise in the mid-infrared which suggests the presence of an obscured active nucleus. The authors have used the infrared-to-optical colors and near-infrared SEDs to infer the properties of the AGN host galaxies. Identifications and photometric parameters for 478 sources detected by XMM-Newton in the ELAIS-S1 field are given. For each source, the X-ray positions and fluxes, optical position and photometry, Spitzer IRAC and MIPS 24 micron positions and fluxes, spectroscopic redshift where available, photometric redshift and SED shape classification are given. This table was created by the HEASARC in December 2008 based on the <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/A+A/488/417">CDS Catalog J/A+A/488/417</a> file catalog.dat. This is a service provided by NASA HEASARC .

Marano Field XMM-Newton X-Ray Source Optical Counterparts

This table contains some of the results from a medium deep XMM-Newton survey of the Marano Field and optical follow-up observations. The mosaicked XMM-Newton pointings in this optical quasar survey field cover 0.6 deg2 with a total of 120 ks good observation time. 328 X-ray sources were detected in total with detection likelihoods ML >= 5. The X-ray fluxes are in the range fX = (0.16 - 54) x 10-14 erg cm-2 s-1 (0.2 - 10 keV). The turnover flux of this sample is fX ~ 5 x 10-15 erg/cm2/s in this same energy band. With VLT FORS1 and FORS2 spectroscopy 96 new X-ray counterparts have been classified. The central 0.28 deg2 region, where detailed optical follow-up observations were performed, contains ~ 170 X-ray sources (detection likelihood ML > 10), out of which 48 had already been detected by ROSAT. In this region 23 out of 29 optically selected quasars have been recovered. With a total of 110 classifications in their core sample, the authors have reached a completeness of ~65%. About one-third of the XMM-Newton sources are classified as type II AGN with redshifts mostly below 1.0. Furthermore, five high redshift type II AGN (2.2 <= z <= 2.8) have been detected. This table contains the list of the 195 optical counterparts for 172 of the XMM-Newton X-ray sources given in Table 8 of the reference paper. It does not contain the full list of 328 X-ray sources given in Table A1 of the reference paper, nor the lists of marginal X-ray sources given in Appendix B of the reference paper. This table was created by the HEASARC in May 2007 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/A+A/466/41">CDS catalog J/A+A/466/41</a> file table8.dat. This is a service provided by NASA HEASARC .

Collinder 261 Chandra X-Ray Source Optical Counterparts Catalog

This table contains some of the results from the first X-ray study of Collinder 261 (Cr 261), which at an age of 7 Gyr is one of the oldest open clusters known in the Galaxy. This observation with the Chandra X-Ray Observatory was aimed at uncovering the close interacting binaries in Cr 261, and reached a limiting X-ray luminosity of LX ~ 4 x 1029 erg s-1 (0.3-7 keV) for stars in the cluster. The authors detected 107 sources within the cluster half-mass radius rh, and they estimate that among the sources with LX >~ 1030 erg s-1, about 26 are associated with the cluster. They identify a mix of active binaries and candidate active binaries, candidate cataclysmic variables, and stars that have "straggled" from the main locus of CR 261 in the color-magnitude diagram. Based on a deep optical source catalog of the field, the authors estimate that Cr 261 has an approximate mass of 6500 Msun, roughly the same as the old open cluster NGC 6791. The X-ray emissivity of Cr 261 is similar to that of other old open clusters, supporting the trend that they are more luminous in X-rays per unit mass than old populations of higher (globular clusters) and lower (the local neighborhood) stellar density. This implies that the dynamical destruction of binaries in the densest environments is not solely responsible for the observed differences in X-ray emissivity. Cr 261 was observed with the Advanced CCD Imaging Spectrometer (ACIS) on board Chandra starting 2009 November 9 14:50 UTC, for a total exposure time of 53.8 ks (ObsID 11308). The observation was made in Very Faint, Timed exposure mode, with a single frame exposure time of 3.2 s. Kharchenko et al. (2013, A&A, 558, A53) estimate that the radius of Cr 261 is ~ 14.1 arcminutes. This is considerably larger than a single ACIS chip (8 4 x 8 4 arcminute2) and therefore the authors placed the center of the cluster (J2000.0 RA = 12h 38m 06.0s, Dec = -68o 22' 01" according to Kharchenko et al. 2013) close to the I3 aimpoint so that a larger contiguous part of the cluster could be imaged (see Figure 1 in the reference paper). The CCDs used were I0, I1, I2, and I3 from the ACIS-I array, and S2 and S3 from the ACIS-S array. The authors limited the X-ray analysis to the data from chips I0, I1, I2, and I3. The S2 and S3 chips lie far from the I3 aimpoint, giving rise to large positional errors on any sources detected on them. Such large errors make it hard to identify optical counterparts, and thus to classify the sources. The authors retrieved optical images of Cr 261 in the B and V bands from the ESO public archive. These data were taken as part of the ESO Imaging Survey (EIS; program ID 164.O-0561). The observations of Cr 261 were made using the Wide Field Imager (WFI), mounted on the 2.2 m MPG/ESO telescope at La Silla, Chile. After correcting the X-ray source positions for the (almost negligible) boresight correction (0.06 =/- 0.07 arcseconds in RA and 0.09 +/- 0.08 arcseconds in Dec), the authors matched their X-ray source list with the entire optical source list, using 95% match radii. For 89 unique X-ray sources, they found 124 optical matches; of the latter, 104 are present in both the V and B images, while for 20 there is only a V or B detection. The authors also inspected the area around each X-ray source in the WFI images by eye, and discovered that five more X-ray sources have candidate optical counterparts that are saturated and therefore missing from their optical catalog. Finally, they added to the list of candidate counterparts six optical sources that lay just outside the 95% match radius, but inside the 3-sigma radius. In total, 98 of the 151 unique X-ray sources were thus matched to one or more optical sources. This HEASARC table contains the list of the 135 optical counterparts to 98 of the 151 X-ray sources from Table 2 of the reference paper. Information about the 151 X-ray sources is available in the HEASARC table CR261CXO (based on Table 1 of the reference paper) to which this current table has links. This table was created by the HEASARC in June 2017 primarily based upon the machine-readable version of Table 2 from the reference paper, the catalog of optical counterparts to Chandra sources in Cr 261, that was obtained from the ApJ web site. The information on the X-ray source positions was taken from the machine-readable version of Table 1 from the reference paper that was also obtained from the ApJ web site. This is a service provided by NASA HEASARC .

M 71 Chandra X-Ray Point Source and Optical/Infrared Counterparts Catalog

The authors observed the nearby, low-density globular cluster M71 (NGC 6838) with the Chandra X-Ray Observatory to study its faint X-ray populations. Five X-ray sources were found inside the cluster core radius, including the known eclipsing binary millisecond pulsar (MSP) PSR J1953+1846A. The X-ray light curve of the source coincident with this MSP shows marginal evidence for periodicity at the binary period of 4.2hr. Its hard X-ray spectrum and luminosity resemble those of other eclipsing binary MSPs in 47 Tuc, suggesting a similar shock origin of the X-ray emission. A further 24 X-ray sources were found within the half-mass radius rh, reaching to a limiting luminosity of 1.5 x 1030 ergs/s (0.3-8 keV). From a radial distribution analysis, the authors find that 18 +/- 6 of these 29 sources are associated with M71, somewhat more than predicted, and that 11 +/- 6 are background sources, both Galactic and extragalactic. M71 appears to have more X-ray sources in the range LX = 1030 - 1031 ergs/s than expected by extrapolating from other studied clusters using either mass or collision frequency. In their paper, the authors explore the spectra and variability of these sources and describe the results of ground-based optical counterpart searches. The authors obtained a 52.4 ks Chandra observation (ObsID 5434) of M71 (nominal center of cluster at J2000.0 RA and Dec of 19 53 46.1 +18 46 42) on 2004 December 20-21 using the Advanced CCD Imaging Spectrometer (ACIS) in very faint (VF), timed-exposure mode with a 3.141s frame time. They searched for X-ray sources in the observed field by employing techniques described in Tennant (2006, AJ, 132, 1372) which use a circular Gaussian approximation to the point-spread function (PSF). Within twice the M71 half-mass radius (rh = 1.65 arcminutes), they set the signal-to-noise threshold (S/N) for detection to 2.0, but also required the number of source counts to be at least 5 times the statistical uncertainty in the local background estimate. The empirical relation derived by Tennant, Cmin = (S/N)2/0.81, then implies a point-source sensitivity limit of about 4.9 counts for rM71 <= 2rh and in the energy band 0.3-8.0 keV. Because of the increase in PSF size with off-axis distance and the associated increase in background within a detection cell, for RM71 > 2rh they set the S/N threshold for detection to 2.4 and again required the number of source counts to be at least 5 times the statistical uncertainty in the local background estimate. The point-source sensitivity limit thus rises to about seven counts. This table contains 63 X-ray sources and their optical/infrared counterpart information, if any, for those sources with rM71 <= 2r_h which are listed in Table 1 of the reference paper: these sources have name prefixes of s01 to s63. It also contains 73 X-ray sources and their optical/infrared counterpart information, if any, for those sources with rM71 > 2r_h which are listed in Table 2 of the reference paper: these sources have name prefixes of ss01 to ss59 and is01 to is14. Each entry in this table corresponds to an X-ray source if there is no counterpart information or only a single identified counterpart or to a particular X-ray source and counterpart match if there are multiple counterpart identifications. There are thus 165 entries in this HEASARC table corresponding to 136 X-ray sources. This table was created by the HEASARC in March 2011 based on the electronic version of Tables 1 and 2 of the reference paper which were obtained from the CDS (their catalog J/ApJ/687/1019 files table1.dat and table2.dat). Some of the values for the alt_name parameter in the HEASARC's implementation of this table were corrected in April 2018. This is a service provided by NASA HEASARC .

Collinder 69 Cluster Optical/IR Counterparts to XMM-Newton X-Ray Point Sources

This table contains some of the results from the first paper of a series devoted to the Lambda Orionis star-forming region, Orion's Head, from the X-ray perspective. The final aim of this research is to provide a comprehensive view of this complex region, which includes several distinct associations and dark clouds. The authors aim to uncover the population of the central, young star cluster Collinder 69, and in particular to find those diskless Class III pre-main sequence objects which have not been identified by previous surveys based on near- and mid-infrared searches, and to establish the X-ray luminosity function for the association. The authors have combined two exposures taken with the XMM-Newton satellite with an exhaustive data set of optical, near- and mid-infrared photometry to assess the membership of the X-ray sources based on different color-color and color-magnitude diagrams, as well as other properties, such as effective temperatures, masses and bolometric luminosities derived from spectral energy distribution fitting and comparison with theoretical isochrones. The presence of circumstellar disks is discussed using mid-infrared photometry from the Spitzer Space Telescope. The authors searched for optical and IR counterparts for their X-ray detections, using a radius of 5.1 arcseconds. This search radius is motivated by the astrometry of XMM-Newton (~ 1-2 arcsec) and the statistical errors of the X-ray sources (<= 4 arcsecs). Multiple counterparts were found for several X-ray sources within their search radius. The visual inspection of all optical and IR images indicated that in a few cases there were additional possible counterparts even slightly beyond this search radius. In order to be as comprehensive as possible, the authors have also retained them. They compiled a master catalog with all sources that were present in at least one of the mappings (optical, near-IR or mid-IR) and extracted the photometry from these surveys. The photometry of all possible counterparts to X-ray sources is listed in this table. The reference sources for the optical and infrared magnitudes are discussed in Section 3 of the reference paper. In this table, they are coded as follows: <pre> Code Reference Source 1 = 2MASS Catalog, <a href="https://cdsarc.cds.unistra.fr/ftp/cats/II/246">CDS Cat. II/246</a> 2 = XMM-Newton Optical Monitor (XMM OM) 3 = Spitzer 4 = Omega 2000 Camera photometry in 2005 5 = CFHT1999 Survey 6 = Barrado y Navascues et al. (2004 ApJ, 610, 1064; 2007 ApJ, 664, 481) 7 = Dolan & Mathieu (1999 AJ, 118, 2409; 2001 AJ, 121, 2124) 8 = Dolan & Mathieu (2002 AJ, 123, 387) 9 = Omega 2000 Camera photometry in 2007 </pre> Thus, this table contains optical and infrared data, as well as membership information, on 205 possible counterparts to the 164 XMM-Newton X-ray sources detected in EPIC observations of the Collinder 69, East and West Fields (C69E and C69W), respectively, with maximum likelihood (ML) values > 15.0. A companion HEASARC Browse table COLL69XMM contains the X-ray data for these X-ray sources. This table was created by the HEASARC in July 2011 based on the electronic versions of Tables 5, 6, 8 and 9 from the reference paper which were obtained from the CDS (their catalog J/A+A/526/A21 files table5.dat, table6.dat, table8.dat and table9.dat). This is a service provided by NASA HEASARC .

Optically Selected Radio-Intermediate and Loud Quasars X-ray Emission Catalog

This catalog contains some of the results of an investigation into the X-ray properties of radio-intermediate and radio-loud quasars (RIQs and RLQs, respectively). The authors have combined large, modern optical (e.g., SDSS) and radio (e.g., FIRST) surveys with archival X-ray data from Chandra, XMM-Newton, and ROSAT to generate an optically selected sample that includes 188 RIQs and 603 RLQs. This sample is constructed independently of X-ray properties but has a high X-ray detection rate (85%); it provides broad and dense coverage of the luminosity-redshift (l-z) plane, including at high redshifts (22% of the objects have z = 2-5), and it extends to high radio-loudness RL values (33% of objects have RL = log(Lr/Lo) = 3 - 5), where Lr and Lo are the rest-frame monochromatic luminosities at 5 GHz and 2500 Angstroms, respectively). The authors measure the "excess" X-ray luminosity of RIQs and RLQs relative to radio-quiet quasars (RQQs) as a function of radio loudness and luminosity, and parametrize the X-ray luminosity of RIQs and RLQs both as a function of optical/UV luminosity and also as a joint function of optical/UV and radio luminosity. RIQs are only modestly X-ray bright relative to RQQs; it is only at high values of radio loudness (RL >~ 3.5) and radio luminosity that RLQs become strongly X-ray bright. This HEASARC table contains the primary sample from the reference paper. The authors consider three categories of quasars in this work: RQQs, RIQs, and RLQs (rather than just RQQs and RLQs), where the define RIQs to consist of objects with 1 <= RL < 2; consequently, the objects they classify as RLQs satisfy RL >= 2. The primary sample contained herein consists of 654 optically selected RIQs and RLQs with SDSS/FIRST observations and high-quality X-ray coverage from Chandra (171), XMM-Newton (202), or ROSAT (281). The primary sample is split nearly evenly between spectroscopic (312) and high-confidence photometric (342) quasars. Most (562) of the primary sample objects possess serendipitous off-axis X-ray coverage, while the remainder (92) were targeted in the observations used in this sample. The X-ray detection fraction for the primary sample is 84%; the detection fraction for those objects with Chandra/XMM-Newton/ROSAT coverage is 95%/92%/70% (typical ROSAT observations are comparatively less sensitive and have higher background). The authors adopt a standard cosmology with H0 = 70 km s-1 Mpc-1, OmegaM = 0.3, and OmegaLambda = 0.7 throughout their study. This table was created by the HEASARC in October 2012 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJ/726/20">CDS Catalog J/ApJ/726/20</a> file table1.dat. This is a service provided by NASA HEASARC .

Swift Simultaneous UV, Optical, and X-Ray Observed Quasar Catalog

The authors have compiled a catalog of optically selected quasars with simultaneous observations in UV/optical and X-ray bands by the Swift Gamma-ray Burst Explorer. Objects in this catalog are identified by matching the Swift pointings with the Sloan Digital Sky Survey (SDSS) Data Release 5 (DR5) quasar catalog. The final catalog contains 843 objects, among which 637 have both Ultraviolet Optical Telescope (UVOT) and X-Ray Telescope (XRT) observations and 354 of which are detected by both instruments. The overall X-ray detection rate is ~ 60% which rises to ~ 85% among sources with at least 10 ks of XRT exposure time. The authors construct the time-averaged spectral energy distribution (SED) for each of the 354 quasars using UVOT photometric measurements and XRT spectra. From model fits to these SEDs, they find that the big blue bump contributes about ~ 0.3 dex to the quasar luminosity. The authors re-visit the alphaox - L2500A relation by selecting a clean sample with only Type 1 radio-quiet quasars; the dispersion of this relation is reduced by at least 15% compared with studies that use non-simultaneous UV/optical and X-ray data. They find only a weak correlation between Lbol/LEdd and alphaUV. They do not find significant correlations between alphax and alphaox, alphaox and alphaUV, and alphax and log L(0.3-10 keV). The correlations between alphaUV and alphax, alphaox and alphax, alphaox and alphaUV, Lbol/LEdd and alphax, and Lbol/LEdd and alphaox are stronger among low-redshift quasars, indicating that these correlations are likely driven by the changes of SED shape with accretion state. This quasar sample was compiled in the following steps: 1. Candidate objects for the catalog were selected as any SDSS DR5 quasar that lie within 20 arcminutes of the center of the Swift FOV in any pointing from launch through 2008 June. 2. XRT data were processed to obtain X-ray count rates, spectra, and spectral parameters. 3. UVOT data were processed to obtain UV and optical photometry. 4. UVOT photometry were supplemented with measurements at other wavelengths from published catalogs. 5. Quasar SEDs were constructed. 6. Additional parameters were calculated based on the SEDs of each quasar. The raw sample is constructed by matching 3.5 years Swift pointings and the SDSS DR5 quasar catalog and contains 1034 objects. This HEASARC version of this catalog contains all 1034 objects in the "raw" catalog. To select only the 843 objects in the "final" catalog, the user should specify catalog_flag = 1 in any searches of this table. This table was created by the HEASARC in August 2012 based on an electronic version of Table 8 from the reference paper which was obtained from the ApJS web site. This is a service provided by NASA HEASARC .

Chandra Serendipitous Extragalactic X-Ray Source ID (SEXSI) Optical Follow-Up

The Serendipitous Extragalactic X-ray Source Identification (SEXSI) Program is designed to expand significantly the sample of identified extragalactic hard X-ray sources at intermediate fluxes, 10-15 ergs/cm2/s < 2-10 keV Flux <~ 10-13 ergs/cm2/s. SEXSI, which includes sources derived from more than 2 square degrees of Chandra images, provides the largest hard X-ray-selected sample yet studied, offering an essential complement to the Chandra Deep Fields (total area of 0.2 square degrees). In Eckart et al. (2005, Paper II) R-band optical imaging of the SEXSI fields from the Palomar P60 and P200, the MDM 2.4m and 1.3m, and the Keck I telescopes is described. The authors have identified counterparts or derived flux limits for nearly 1000 hard X-ray sources. Using the optical images, they have derived accurate source positions. They have investigated correlations between optical and X-ray flux, and optical flux and X-ray hardness ratio. They have also studied the density of optical sources surrounding X-ray counterparts, as well as the properties of optically faint, hard X-ray sources. In Eckart et al. (2006, Paper III) optical spectra of 477 counterparts are presented. These spectra reach to R-band magnitudes of <~24 and have produced identifications and redshifts for 438 hard X-ray sources. Typical completeness levels in the 27 Chandra fields studied are 40-70%. The vast majority of the 2-10 keV selected sample are AGNs with redshifts between 0.1 and 3; the highest redshift source lies at z = 4.33. This table which combines data presented in Eckart et al. (2005, 2006) has links to the list of SEXSI X-ray sources (the HEASARC Browse table CHANSEXSI: see Paper I = Harrison et al. 2003, ApJ, 596, 944). This table was originally created by the HEASARC in June 2005 based on the CDS version of Table 3 from Eckart et al. (2005: CDS table J/ApJS/156/35/table3.dat). It was updated in August 2006 to include information from Table 2 of Eckart et al. (2006: the electronic version available at the electronic ApJ web site). This is a service provided by NASA HEASARC .